Introduction to Networkspython4csip.com/files/download/Introduction to computer Networks.pdfhardware crash or any other) them its other copy can be used. Cost Factor :- Cost factor

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CREATED BY: SACHIN BHARDWAJ, PGT (CS) KV NO.1 TEZPUR, MR. VINOD KUMAR VERMA, PGT (CS) KV OEF KANPUR

Unit-3

Introduction to Computer Networks

Introduction to Networks

The collection of interconnected computers is called a computer

network. Two computers are said to be interconnected if they are

capable of sharing and exchanging information.

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Need of Computer Network

Resource Sharing :- Resource Sharing means to make all programs,

data and peripherals available to anyone on the network irrespective

of the physical location of the resources and the user.

Reliability :- Reliability means to keep the copy of a file on two or more

different machines, so if one of them is unavailable (due to some

hardware crash or any other) them its other copy can be used.

Cost Factor :- Cost factor means it greatly reduces the cost since the

resources can be shared.

Application of Computer

Networks

1. Sharing of data, services and resources

2. Access to remote database

3. Communication facilities

Elementary Terminology of Networks :-

1. Nodes (Workstations):- The term nodes refer to the computers that

are attached to a network and are seeking to share the resources.




2. Server:- A computer that facilitates the sharing of data, software

and hardware resources on the network.

Types of Computer

Networks

LAN (Local Area Network): A Local Area Network (LAN) is a network

that is limited to a relatively small area. It is generally limited to a

geographic area such as writing lab, school or building. It is generally

privately owned networks over a distance not more than 5 Km. e.g.

network in a college, school, hospital etc.




MAN (Metropolitan Area Network): MAN is the networks that

cover a group of nearby corporate offices or a city and might be either

private or public. E.g. Cable TV Network in a city.

WAN (Wide Area Network): These are the networks spread over

large distances, say across countries or even continents through

cabling or satellite uplinks are called WAN. E.g. Internet




PAN (Personal Area Network): A PAN is a network of

communicating devices (Computer, Phone, MP3/MP4 Player, Camera

etc.) organized around an individual person. A PAN can be set up

using guided media (USB cable) or unguided media (Bluetooth,

Infrared).

Network Devices

1. Modem:-A modem (modulator/demodulator) is a hardware

device that allows a computer to send and receive information over

telephone lines. When sending a signal, the modem converts

(modulates) digital data to an analog signal and transmit it over a

telephone line. Similarly when an analog signal is received, the

modem converts it back (demodulates) to a digital signal.

2. Hub :- A Hub is an electronic device that connects several

nodes to form a network and redirects the received information to

all the connected nodes in broadcast mode. The computer(s) for

which the information is intended receive(s) this information and

accept(s) it. Other computers on the network simply reject this

information.




Types of Hub-

Passive Hub: This type of does not amplify or boost the signal. It

does not manipulate or view the traffic that crosses it.

Active Hub: It amplifies the incoming signal before passing it to the other

ports.

3. Switch :- A switch is a network device which is used to

interconnect computers or devices on a network. It filters and

forwards data packets across a network. The main difference between

hub and switch is that hub replicates what it receives on one port onto

all the other ports while switch keeps a record of the MAC addresses

of the devices attached to it and forwards data packets onto the ports

for which it is addressed across a network, that’s why switch is

intelligent Hub.




Diagram of A 4-Port Switch

4. Repeater :- A Repeater is a device that is used to amplify and

regenerate a signal which is on its way through a communication

channel. A repeater regenerates the received signal and re-transmits

it to its destination.

5. Router :- A device that forwards data packets from one network

to another by finding the shortest route, based on an internal routing

table and the address of the destination network in the incoming

packet, the router determines whether to send the packet out or keep

it within the network.




Gateway :- A gateway is a device that connects dissimilar networks.




Network Topologies

Bus Topology :-Bus topology is a topology for a Local Area

Network (LAN) in which all the nodes are connected to a single cable.

The starting and ending point of cable is called terminator.

ADVANTAGES

• It is easy to install.

• It requires less cable length and hence it is cost effective.

• Failure of a node does not affect the network.

DISADVANTAGES

• In case of cable or terminator fault, the entire network breaks

down.

• Not suitable for large number of computers.

• At a time only one node can transmit data.




The STAR Topology: -

A STAR topology is based on a central node which acts as a hub. A

STAR topology is common in homes networks where all the

computers connect to the single central computer using it as a hub.

Advantages:

• Easy to troubleshoot

• A single node failure does not affect the entire network.

• Fault detection and removal of faulty parts is easier.

• In case a workstation fails, the network is not affected.

Disadvantages:-

• Difficult to expand.

• Longer cable is required.




• The cost of the hub and the longer cables makes it expensive

over others.

• In case hub fails, the entire network

TREE Topology

It has a root node and all other nodes are connected to it forming a

hierarchy. It is also called hierarchical topology. It should at least have

three levels to the hierarchy.

Features of Tree Topology

• Ideal if workstations are located in groups.

• Used in Wide Area Network.

Advantages of Tree Topology

• Extension of bus and star topologies.

• Expansion of nodes is possible and easy.

• Easily managed and maintained.




• Error detection is easily done

Disadvantages of Tree Topology

• Heavily cabled.

• Costly.

• If more nodes are added maintenance is difficult.

• Central hub fails, network fails.

Mesh Topology :-

Mesh topology is a group of nodes which are all connected to each

other and many types of connections are possible in a mesh topology.




Advantage of Mesh Topology

• The arrangement of the network nodes is such that it is

possible to transmit data from one node to many other

nodes at the same time.

• Fault is diagnosed easily.

Disadvantage of Mesh Topology

• Installation and configuration is difficult.

• Cabling cost is more.

• Bulk wiring is required.

Introduction to Internet

The Internet is a massive network of networks, a networking

infrastructure. It connects millions of computers together globally,

forming a network in which any computer can communicate with

another computer as long as they are both connected to the Internet.

The World Wide Web, or simply Web is a way or medium of accessing

information over the Internet. It is an information sharing model that

is built on top of the Internet.




” The Internet emerged in the United States in the 1970s but did not

become visible to the general public until the early 1990s. By 2020,

approximately 4.5 billion people, or more than half of the world’s

population, were estimated to have access to the Internet”.

The Internet provides a capability so powerful and general that it can

be used for almost any purpose that depends on information, and it

is accessible by every individual who connects to one of its associated

networks.

URL :- URL stands for Uniform Resource Locator. A URL is nothing

more than the address of a given unique resource on the Web or

address of a website. The URL is an address that matches users to a

specific resource online, such as webpage.

Example- http://www.python4csip.com




WWW : The World Wide WEB (WWW), commonly known as the ‘Web’.

It is an information system all the web resources are identified by

Uniform Resource Locator (URL). Tim Berners-Lee invented the WWW

in 1989. He wrote the first web browser in 1990.

Application of WWW :

• Publishing, Marketing and advertising

• Research and Development

• Communication

• Collaboration

• Industrial classification of the sample companies etc.

• Gaming

e-mail: email (or e-mail) is defined as the transmission of messages

over communications networks. Typically the messages are notes

entered from keyboard and sent over internet using computer or

mobile.

Chat : Chat may refer to any kind of communication over the

Internet that offers a real-time transmission of text messages from

sender to receiver. Chat messages are generally short in order to

enable other participants to respond quickly.




Voip :- Voice over Internet Protocol (VoIP), is a technology that allows

you to make voice calls using a broadband Internet connection

instead of a regular (or analog) phone line. VoIP services convert your

voice into a digital signal that travels over the Internet. If you are

calling a regular phone number, the signal is converted to a regular

telephone signal before it reaches the destination. VoIP can allow you

to make a call directly from a computer

Website :- a website is a group of web pages, containing text,

images and all types of multi-media files.

Difference between Website and Webpage :-

Website Webpage

A collection of web pages which

are grouped together and usually

connected together in various

ways. Often called a "web site" or

simply a "site."

A document which can be

displayed in a web browser such

as Firefox, Google Chrome,

Opera, Microsoft Internet

Explorer etc.




Difference between Static and Dynamic webpage :-

Statics Webpage Dynamic Webpage

The static web pages display the

same content each time when

someone visits it

Dynamic web pages the page

content changes according to

the user.

It takes less time to load over

internet.

Dynamic web pages take more

time while loading.

No Database used. A database is used in at the

server end in a dynamic web

page.

Web Server :- a web server is a computer that stores web server

software and a website's component files (e.g. HTML documents,

images, CSS style sheets, and JavaScript files).

When client sends request for a web page, the web server search

for the requested page if requested page is found then it will send it

to client with an HTTP response. If the requested web page is not

found, web server will the send an HTTP response :Error 404 Not

found.




Web Hosting :- Web hosting is an online service that enables you

to publish your website or web application on the internet. When you

sign up for a hosting service, you basically rent some space on a

server on which you can store all the files and data necessary for your

website to work properly.

A server is a physical computer that runs without any interruption so

that your website is available all the time for anyone who wants to see

it.

Web Browswer :- A web browser, or simply "browser," is an

application used to access and view websites. Common web browsers

include Microsoft Internet Explorer, Google Chrome, Mozilla Firefox,

and Apple Safari.

Plug-ins:- a plug-in (or plugin, add-in, add-on) is a software

component that adds a specific feature to an existing computer

program. When a program supports plug-ins, it enables

customization. Plug-ins are commonly used in Internet browsers but

also can be utilized in numerous other types of applications.

Add-ons : An Add-on is either a hardware unit that can be added to

a computer to increase the capabilities or a program unit that

enhances primary program. Some manufacturers and software

developers use the term add-on.


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Examples of add-ons for a computer include card for sound,

graphic acceleration, modem capability and memory. Software add-

ons are common for games, word-processing and accounting

programs.

Cookies :- cookies are small files which are stored on a user’s

computer and contains information like which Webpages visited in

the past, logging details Password etc. They are designed to hold a

modest amount of data specific to a particular client and website and

can be accessed by the web server or the client computer.


Documents

Introduction to Networkspython4csip.com/files/download/Introduction to computer Networks.pdfhardware crash or any other) them its other copy can be used. Cost Factor :- Cost factor